
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
March 27th, 2012, 05:46 PM  #1 
Newbie Joined: Jan 2012 Posts: 28 Thanks: 0  Prove the difference between numbers
The sum of the digits of a twodigit prime number is subtracted from the number. Prove that the difference cannot be a prime number.

March 27th, 2012, 06:47 PM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: Prove the difference between numbers
Let A be the tens place digit and B be the units digits, the the difference is: Since 9 is composite, so must 9A be composite. 

Tags 
difference, numbers, prove 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
First proof!  The difference of two numbers is scalable  ryanninjasheep  Applied Math  1  February 28th, 2014 03:55 PM 
Prove: difference of two sets  toughcookie723  Applied Math  4  November 17th, 2011 08:37 AM 
prove the floor of two numbers is the same as....  finalight  Number Theory  7  September 14th, 2011 07:28 AM 
Find two numbers where difference is 20 & the sum is 4  sharp  Elementary Math  7  October 30th, 2010 08:52 AM 
Prove: difference of two sets  toughcookie723  Number Theory  3  December 31st, 1969 04:00 PM 